[Autonomous intrathoracic goiter. Apropos of 2 new cases].

An autonomous intrathoracic goiter (AIG) is a thyroid gland formation located in the thorax or, more precisely, the mediastinum. It is not a metastasis of thyroid cancer, and it has no parenchymatous or vascular connections with the cervical thyroid gland. It is fed by thoracic vessels and is observed in the absence of previous thyroidectomy. Its multiple appellations, and the fact that clinical reports often lack precision and detail, complicate investigations concerning AIG, a rare variety of mediastinal goitre (slightly more than 100 cases published). AIG is essentially caused by an abnormal embryonic development of the thyroid gland. It must be distinguished from migratory goitres partially resected and forgotten in the thorax after cervicotomy. This fully mediastinal tumour is usually removed by the thoracic approach.